Method for making carbon fiber film

ABSTRACT

A method for making carbon fiber film includes drawing a carbon nanotube film from a carbon nanotube array. The carbon nanotube film is successively passed through a first room and a second room. A carrier gas and a carbon source gas are supplied to the first room and a carbon layer is formed on the carbon nanotube film located in the first room. The carbon nanotube film with the carbon fiber film is taken into the second room from the first room, and the carbon layer is graphitized.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims all benefits accruing under 35 U.S.C. § 119 fromChina Patent Application No. 201410358049.4, filed on Jul. 25, 2014, inthe China Intellectual Property Office. This application is related tocommonly-assigned application entitled, “CARBON FIBER FILM”,concurrently filed Ser. No. 14/526,459; “CATHODE OF LITHIUM-IONBATTERY”, concurrently filed Ser. No. 14/526,458); “MEMBRANE ELECTRODEASSEMBLY OF FUEL CELL”, concurrently filed Ser. No. 14/526,456.Disclosures of the above-identified applications are incorporated hereinby reference.

FIELD

The present application relates to a method for making carbon fiberfilm, and particularly to a method for making a vapor grown carbon fiberfilm.

BACKGROUND

Vapor grown carbon fibers (VGCFs) have a high specific strength, aspecific modulus, and a crystalline orientation. In addition, VGCFs havegood electrical conductivity, and thermal conductivity. Thus, VGCFs haveattracted much attention in recent years.

VGCFs is conventionally prepared by catalytic cracking a hydrocarboncompound and vapor depositing on transition metal, such as iron, cobalt,nickel, or any combination alloy thereof. In detail, a substrate islocated into a reaction tube, wherein the substrate is coated a metalgranule layer acted catalyst, and then a mixing gas including ahydrocarbon and a hydrogen is supplied into the reaction tube, finallyVGCFs are grown on the substrate. However, above-described method formaking VGCFs is difficult to continuous and batch production.

What is needed, therefore, is to provide a method for making carbonfiber film that can overcome the above-described shortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures, wherein:

FIG. 1 is a schematic view of one embodiment of a device using formaking a carbon fiber film.

FIG. 2 is a scanning electron microscope (SEM) image of a carbonnanotube film.

FIG. 3 is a schematic view of another embodiment of a device using formaking the carbon fiber film.

FIG. 4 is a schematic view of one embodiment of the carbon fiber film.

FIG. 5 is a three-dimensional schematic view of one carbon fiber of thecarbon fiber film of FIG. 4.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures and components have notbeen described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale andthe proportions of certain parts may be exaggerated to better illustratedetails and features. The description is not to be considered aslimiting the scope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now bepresented.

The term “coupled” is defined as connected, whether directly orindirectly through intervening components, and is not necessarilylimited to physical connections. The connection can be such that theobjects are permanently connected or releasably connected. The term“outside” refers to a region that is beyond the outermost confines of aphysical object. The term “inside” indicates that at least a portion ofa region is partially contained within a boundary formed by the object.The term “substantially” is defined to be essentially conforming to theparticular dimension, shape or other word that substantially modifies,such that the component need not be exact. For example, substantiallycylindrical means that the object resembles a cylinder, but can have oneor more deviations from a true cylinder. The term “comprising” means“including, but not necessarily limited to”; it specifically indicatesopen-ended inclusion or membership in a so-described combination, group,series and the like.

Referring to FIG. 1, a method for making a carbon fiber film of oneembodiment includes the following steps:

(S10), providing a carbon nanotube array 10;

(S20), forming a carbon nanotube film 20 by pulling from the carbonnanotube array 10, and making the carbon nanotube film 20 successivelypass through a first room 30 and a second room 40;

(S30), supplying a carrier gas and a carbon source gas to the first room30 and forming a carbon layer 52 on the carbon nanotube film 20 locatedin the first room 30 by controlling a temperature of the first room 30,wherein the carbon nanotube film 20 and the carbon layer 52 form acarbon nanotube composite film; and

(S40), taking the carbon nanotube composite film into the second room 40from the first room 30, and graphitizing the carbon layer 52 bycontrolling a temperature of the second room.

In the step (S10), the carbon nanotube array 10 can be a super-alignedarray formed by a chemical vapor deposition method. The chemical vapordeposition method for making the carbon nanotube array generallyincludes the following steps:

(S11), providing a substrate 12, wherein the substrate 12 can be asubstantially flat and smooth silicon substrate with a diameter of 4inches, and the silicon substrate can be a P-type silicon wafer, anN-type silicon wafer or a silicon wafer formed with an oxidized layerthereon. In one embodiment, a 4-inch, P-type silicon wafer is used asthe substrate 12.

(S12), forming a catalyst layer on the substrate 12, wherein thecatalyst layer is made of a material selected from the group consistingof iron (Fe), cobalt (Co), nickel (Ni), and an alloy thereof. In oneembodiment, the catalyst layer is Fe;

(S13), annealing the substrate 12 with the catalyst layer in air at atemperature in a range from 700° C. to 900° C. for about 30 minutes toabout 90 minutes; and

(S14), providing a carbon source gas at high temperature to a furnacefor about 5 minutes to about 30 minutes to grow the carbon nanotubearray 10 on the substrate 12, wherein the substrate 12 has been put inthe furnace which has been heated to a temperature of 400° C.-740° C.and is filled with a protective gas. The carbon source gas can be, e.g.,methane, ethylene, propylene, acetylene, methanol, ethanol, or a mixturethereof. The protective gas can, preferably, be made up of at least oneof nitrogen (N2), ammonia (NH3), and a noble gas in the presentembodiment.

Moreover, the carbon nanotube array 10 formed under the above conditionsis essentially free of impurities such as carbonaceous or residualcatalyst particles. The carbon nanotube array 10 includes a plurality ofcarbon nanotubes parallel to each other and perpendicular to a topsurface of the substrate 12.

In the step (S20), the carbon nanotube film 20 is obtained by extractinga portion of the carbon nanotube array 10 by the substeps of:

(S21), selecting some carbon nanotube segments of the carbon nanotubearray 10 having a determined width, and then using a drawing tool withthe predetermined width to secure the end of the carbon nanotubesegments of the carbon nanotube array 10; and

(S22), pulling the drawing tool away from the carbon nanotube at aneven/uniform speed to make the carbon nanotube segments of the carbonnanotube array 10 separate from the carbon nanotube array 10.

In the step (S22), the pulling direction can be substantiallyperpendicular to the growing direction of the carbon nanotube array 10.The drawing tool can be a nipper, a clamp, an adhesive tape, and so on.

In the step (S22), during the extracting process, when the end of thecarbon nanotube segments of the carbon nanotubes of the carbon nanotubearray 10 is drawn out, other carbon nanotube segments are also drawn outin a manner that ends of a carbon nanotube is connected with ends ofadjacent carbon nanotubes, by the help of the van der Waals attractiveforce between the ends of carbon nanotube segments. This characteristicof the carbon nanotubes ensures that a continuous carbon nanotube film20 can be formed.

A width of the carbon nanotube film 20 is related to a size of thecarbon nanotube array 10. A length of the carbon nanotube film 20 can beselected according to need. In one embodiment, when the carbon nanotubearray 10 is 4-inch, the width of the carbon nanotube film 20 is in arange from about 0.5 nanometers to about 10 centimeters, and a thicknessof the carbon nanotube film 20 is in a range from about 0.5 nanometersto about 10 microns.

Referring to FIG. 2, the carbon nanotube film 20 includes a plurality ofcarbon nanotubes uniformly distributed therein. The plurality of carbonnanotubes can be combined by van der Waals attractive force. The carbonnanotube film 20 can be a substantially pure structure of the carbonnanotubes, with few impurities. The plurality of carbon nanotubes may besingle-walled, double-walled, multi-walled carbon nanotubes, or theircombinations. The carbon nanotubes which are single-walled have adiameter of about 0.5 nanometers (nm) to about 50 nm. The carbonnanotubes which are double-walled have a diameter of about 1.0 nm toabout 50 nm. The carbon nanotubes which are multi-walled have a diameterof about 1.5 nm to about 50 nm.

The carbon nanotube film 20 is a free-standing film. The term“free-standing” includes, but not limited to, the carbon nanotube film20 that does not have to be supported by a substrate. For example, thefree-standing carbon nanotube film 20 can sustain the weight of itselfwhen it is hoisted by a portion thereof without any significant damageto its structural integrity. So, if the free-standing carbon nanotubefilm 20 is placed between two separate supporters, a portion of thefree-standing carbon nanotube film 20, not in contact with the twosupporters, would be suspended between the two supporters and yetmaintain film structural integrity.

The first room 30 can define a first inlet opening 32 and a first outletopening 34 opposite to the first inlet opening 32. The second room 40can define a second inlet opening 42 and a second outlet opening 44opposite to the second inlet opening 42. The carbon nanotube film 20 issuccessively pass through entire first room 30 and entire second room 40by using the drawing tool, and fixed on a supporting shaft 60, as shownin FIG. 1. The supporting shaft 60 can rotate around its axis, thecarbon nanotube film 20 can be collected on the supporting shaft 60.

In the step (S30), forming the carbon layer 52 on the carbon nanotubefilm 20 includes the following steps:

(S31), supplying the carrier gas to the first room 30;

(S32), supplying the carbon source gas to the first room 30; and

(S33), heating the first room 30 to a temperature from about 800 degreesCelsius to about 1000 degrees Celsius, and cracking the carbon sourcegas to form a plurality of amorphous carbons, wherein the plurality ofamorphous carbons is deposited on the carbon nanotube film 20 in thefirst room 30.

In the step (S31), the first room 30 can be purified by the carrier gas.The carrier gas includes nitrogen, ammonia, or inert gas, such as argon.A flow speed of the carrier gas can range from about 50 sccm to about100 sccm.

In the step (S32), the carbon source gas can be a hydrocarbon compound,such as alkyne. A flow speed of the carrier gas can range from about 20sccm to about 100 sccm.

In the step (S33), a heater 70 surrounds the first room 30 and heats thefirst room 30 to the temperature from about 800 degrees Celsius to about1000 degrees Celsius. In one embodiment, when a time of supplying thecarbon source gas ranges from about 30 minters to about 60 minters, athickness of the carbon layer 52 ranges from about 5 nanometers to about10 microns. In order to uniformly cover the carbon nanotube film 20 andenclose each of the plurality of carbon nanotubes, the thickness of thecarbon layer 52 is greater than or equal to 5 nanometers. The thicknessof a composite structure including the carbon layer 52 and the carbonnanotube film 20 is greater than or equal to 30 nanometers.

In the process of forming the carbon layer 52, a pressure in the firstroom 30 can be in a range from about 50 Pa to about 1000 Pa. The carbonnanotube film 20 cannot be destroyed because the inert gas is in thefirst room 30 and the pressure in the first room 30 ranges from about 50Pa to about 1000 Pa.

The carrier gas and the carbon source gas can be simultaneously suppliedto the first room 30. At this time, the flow speed of the carrier gasranges from about 10 sccm to about 50 sccm. In one embodiment, thecarrier gas and the carbon source gas are simultaneously supplied to thefirst room 30, the flow speed of the carrier gas is 25 sccm, and theflow speed of the carbon source gas is 50 sccm.

The carbon nanotube film 20 defines a plurality of micropores, which isformed by two adjacent carbon nanotubes of the carbon nanotube film 20.The plurality of amorphous carbons formed by cracking the carbon sourcegas is deposited on a surface of the plurality of carbon nanotubes, anddeposited in the plurality of micropores. The carbon layer 52 thusencloses each of the plurality of carbon nanotubes.

In the step (S40), the supporting shaft 60 is rolled, and the carbonnanotube film 20 continues to be pulled from the carbon nanotube array10. The carbon nanotube composite film in the first room 30 is passedthrough the first outlet opening 34 and the second inlet opening 42 andinto the second room 40.

There is a vacuum in the second room 40. A pressure in the second room40 ranges from about 50 Pa to about 1000 Pa. The heater 70 surrounds thesecond room 40 and heats the second room 40 to a temperature from about2000 degrees Celsius to about 3000 degrees Celsius. The carbon layer 52thus is graphitized. A plurality of carbons of the carbon layer 52 ischanged to SP² hybrid structure joined with covalent bond fromamorphous. The carbon nanotube film 20 cannot be destroyed in the secondroom 40 because the vacuum is in the second room 40. The plurality ofcarbon nanotubes of the carbon nanotube film 20 is SP² hybrid graphenelayer structure. Original structure defects of the plurality of carbonnanotubes in the carbon nanotube film 20 can be repaired by heating inthe vacuum. In the process of forming the carbon layer 52 andgraphitizing carbon layer 52, the pressure in the first room 30 and thesecond room 40 can be normal pressure. The normal pressure can be 101000Pa. When the carbon layer 52 is formed in normal pressure, the carbonsource gas and the inert gas can protect the carbon layer 52 fromdamage. When the carbon layer 52 is graphitized in normal pressure, theinert gas can protect carbon structure of the carbon fiber film 50.

In one embodiment, when the thickness of the carbon layer 52 is greaterthan a diameter of the plurality of carbon nanotubes, after graphitizingthe carbon layer 52 to form a plurality of graphene sheets, it isdifficult for the graphene sheets to be parallel to extending directionsof the carbon nanotubes. Therefore, an angle can be formed between eachgraphene sheet and each carbon nanotube. In one embodiment, thethickness of the carbon layer 52 is greater than or equal to 100nanometers.

A length of the plurality of graphene sheets is greater than thediameter of the plurality of carbon nanotubes and in a range from about50 nanometers to about 10 microns. A width of the plurality of graphenesheets is in a range from about 10 nanometers to about 20 nanometers. Atime for graphitizing the carbon layer 52 is related to the thickness ofthe carbon layer 52. The greater the thickness of the carbon layer 52,the longer the time lasts. In one embodiment, the thickness of thecarbon layer 52 is in a range from about 100 nanometers to about 10microns, the time for graphitizing the carbon layer 52 is in a rangefrom about 20 minutes to about 60 minutes.

The carbon layer 52 is graphitized to the plurality of graphene sheets,and the plurality of graphene sheets is joined with the carbon nanotubefilm 20, thus the carbon fiber film 20 is formed.

The supporting shaft 60 is rolled along the direction of pulling thecarbon nanotube film 20, and the carbon nanotube film 20 continues to bepulled from the carbon nanotube array 10, at the same time the carbonlayer 52 in the first room 30 is passed through the first outlet opening34 and the second inlet opening 42 and into the second room 40 andgraphitized in the second room 40.

It is to be understood that, in one embodiment, when rolling thesupporting shaft 60 along the direction of pulling the carbon nanotubefilm 20, the carbon nanotube film 20 is formed by pulling from thecarbon nanotube array 10, while the carbon layer 52 is formed on thecarbon nanotube film 20 and then graphitized, and at the same time thecarbon fiber film 50 is rolled to the supporting shaft 60. Therefore,the carbon fiber film 50 can achieve continuous and batch production.

The supporting shaft 60 can be rolled along a direction substantiallyperpendicular to the pulling direction of the carbon nanotube film 20,and the carbon fiber film 50 thus is twisted to a string structure,improving the mechanical strength of the carbon fiber film 20.

In the process of forming and graphitizing the carbon layer 52, thecarbon nanotube film 20 is suspended. The carbon nanotube film 20 has afirst end and a second end opposite to the first end, the first end ofthe carbon nanotube film 20 is connected to the carbon nanotube array10, and the second end of the carbon nanotube film 20 is held by thesupporting shaft 60. The supporting shaft 60 can be fixed on a rotatingmachine to pull and rotate simultaneously.

Referring to FIG. 3, an embodiment of the method for making the carbonfiber film 50 is shown where a plurality of carbon nanotube films 20 arerespectively pulled from a plurality of carbon nanotube arrays 10, and acarbon layer 52 is formed on each of the plurality of carbon nanotubefilms 20 and then graphitized. Thus, a plurality of carbon fiber films50 can be simultaneously formed, improving yield of the carbon fiberfilm 50.

After forming the carbon fiber film 50, a plurality of conductiveparticles can be deposited on the carbon fiber film 50, furtherimproving the electrical conductivity of the carbon fiber film 50. Theplurality of conductive particles can be deposited on the surface of theplurality of carbon nanotubes 56 and the surface of the plurality ofgraohene sheets 58. The plurality of conductive particles includes alloynanoparticles, metal-oxide nanoparticles, graphite oxide compositenanoparticles, or their combinations. The alloy nanoparticle may beCu₆Sn₅, Mg₂Sn, CoSn, NiSn₄, CeSn₃, or their combinations. Themetal-oxide nanoparticle may be SnO₂, Fe₂O₃, CoO, CuO, NiO₂, or theircombinations. The graphite oxide composite nanoparticles may becomposites of the graphite oxide and metal-oxide nanoparticles asdescribed above. The nanoparticles have diameters of about 1 nanometer(nm) to about 50 nm. In one embodiment, the nanoparticles are SnO₂ andhave diameters of about 2 nm to about 3 nm.

Referring to FIGS. 4 and 5, the carbon fiber film 50 is a membranestructure. The carbon fiber film 50 includes a plurality of carbonnanotubes 56 and a plurality of graphene sheets 58. The plurality ofcarbon nanotubes 56 are joined end to end by van der Waals attractiveforce and extend along a same direction. Each of the plurality of carbonnanotubes 56 is surrounded by the plurality of graphene sheets 58. Partof edge of each of the plurality of graphene sheets 58 is joined withthe carbon nanotube 56 by covalent bond. An angle is between eachgraphene sheet 58 and an outside wall of the carbon nanotube 56. Theplurality of graphene sheets 58 are interval distribution on the outsidewall of the carbon nanotube 56, and a distance between two adjacentgraphene sheets is arbitrary. The length of the plurality of graphenesheets 58 is greater than the diameter of the carbon nanotube 56 andranges from about 50 nanometers to about 10 microns. The width of theplurality of graphene sheets 58 is similar to the diameter of the carbonnanotube 56 and ranges from about 10 nanometers to about 20 nanometers.An extending length of each graphene sheet 58 is 2.5 times −100 times aslong as the diameter of the carbon nanotube 56.

The carbon fiber film 50 includes a plurality of carbon fibers 54 joinedend to end. The plurality of carbon fibers 54 extends along a samedirection. Each carbon fiber 54 includes a carbon nanotube 56 and theplurality of graphene sheets 58. The plurality of graphene sheets 58forms a graphene layer. Two adjacent carbon fibers 54 are joined by vander Waals attractive force. In the carbon fiber film 50, two adjacentcarbon fibers 54 side by side may be spaced apart from each other. Poresare defined in the carbon fiber film 50 by adjacent carbon fibers 54.

The plurality of carbon nanotubes 56 is uniformly distributed andsubstantially parallel to a surface of the carbon fiber film 50. Thecarbon fiber film 50 is a free-standing film and can bend to desiredshapes without breaking.

The angle between each graphene sheet 58 and the carbon nanotube 56 canrange from about 0 degrees to about 90 degrees. In one embodiment, theangle between each graphene sheet 58 and the carbon nanotube 56 is in arange from about 30 degrees to about 60 degrees. In one embodiment, theangles between each graphene sheet 58 and the carbon nanotube 56 areequal to 45 degrees, as shown in FIG. 4. A diameter of each carbon fiber54 is related to the thickness of the carbon layer 52. The diameter ofthe plurality of carbon fibers 54 can be in a range from about 450nanometers to about 100 microns. In one embodiment, the diameter of theplurality of carbon fibers 54 is about 500 nanometers.

The carbon fiber film 50 can include at least two stacked carbonnanotube films 20, adjacent carbon nanotube films 20 can be combined byonly the van der Waals attractive force therebetween. Additionally, anangle between the extending directions of the carbon nanotubes in twoadjacent carbon nanotube films 20 can be in a range from about 0 degreesto about 90 degrees. Stacking the carbon nanotube films 20 will improvethe mechanical strength of the carbon fiber film 50. In one embodiment,the carbon fiber film 50 includes two layers of the carbon nanotubefilms 20, and the angle between the extending directions of the carbonnanotubes in two adjacent carbon nanotube films 20 is about 90 degrees.

The carbon fiber film 50 has good electrical conductivity. A sheetresistance of the carbon fiber film 50 is less than or equal to 100 ohm.Two adjacent carbon nanotubes 56 are joined end to end by combining agraphene sheet 58, and the graphene sheet 58 is combined with the twoadjacent carbon nanotubes 56 by the covalent bond. Therefore, themechanical strength of the carbon fiber film 50 is further improved.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, including inmatters of shape, size and arrangement of the parts within theprinciples of the present disclosure up to, and including, the fullextent established by the broad general meaning of the terms used in theclaims.

Additionally, it is also to be understood that the above description andthe claims drawn to a method may include some indication in reference tocertain steps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A method for making carbon fiber film comprising:drawing a carbon nanotube film from a carbon nanotube array, and makingthe carbon nanotube film successively pass through a first room and asecond room; supplying a carrier gas and a carbon source gas to thefirst room and forming a carbon layer on the carbon nanotube filmlocated in the first room; and taking the carbon nanotube film with thecarbon layer into the second room from the first room, graphitizing thecarbon layer, wherein the carbon nanotube film is suspended in a processof graphitizing the carbon layer; and the carbon nanotube film comprisesa first end and a second end opposite to the first end, in the processof graphitizing the carbon layer, the first end is connected to thecarbon nanotube array, and the second end is held by a supporting shaft.2. The method of claim 1, wherein in a process of the forming the carbonlayer, the carbon nanotube film is suspended.
 3. The method of claim 2,wherein the first end of the carbon nanotube film is connected to thecarbon nanotube array, and the second end of the carbon nanotube film isheld by the supporting shaft.
 4. The method of claim 1, wherein theforming the carbon layer comprises: supplying the carrier gas to thefirst room; supplying the carbon source gas to the first room; andheating the first room to a temperature from about 800 degrees Celsiusto about 1000 degrees Celsius, and cracking the carbon source gas toform a plurality of amorphous carbons, wherein the plurality ofamorphous carbons is deposited on the carbon nanotube film in the firstroom.
 5. The method of claim 4, further comprising depositing theplurality of amorphous carbons on a surface of a plurality of carbonnanotubes of the carbon nanotube film, and in a plurality of microporesformed by adjacent carbon nanotubes.
 6. The method of claim 5, whereinthe carbon layer encloses each of the plurality of carbon nanotubes. 7.The method of claim 1, wherein a thickness of the carbon layer isgreater than or equal to 5 nanometers.
 8. The method of claim 1, whereina thickness of the carbon layer is greater than or equal to 100nanometers.
 9. The method of claim 1, wherein the carbon nanotube filmsuccessively passes through the entire first room and the entire secondroom by using a drawing tool, and the carbon nanotube film is fixed on asupporting shaft.
 10. The method of claim 9, wherein when the supportingshaft is rolled, the carbon nanotube film continues to be pulled fromthe carbon nanotube array, and the carbon nanotube film with the carbonlayer in the first room is pulled into the second room.
 11. The methodof claim 1, wherein a pressure in the first room is in a range fromabout 50 Pa to about 1000 Pa.
 12. The method of claim 1, wherein apressure in the second room is in a range from about 50 Pa to about 1000Pa.
 13. The method of claim 1, wherein the carbon layer is graphitizedto form a plurality of graphene sheets joined with the carbon nanotubefilm by a covalent bond.
 14. The method of claim 1, further comprisingdepositing a plurality of conductive particles after graphitizing thecarbon layer.
 15. A method for making carbon fiber film comprising:drawing a carbon nanotube film from a carbon nanotube array; forming acarbon layer on the carbon nanotube film by cracking a carbon sourcegas; and graphitizing the carbon layer, wherein the carbon nanotube filmis suspended in a process of forming and graphitizing the carbon layer;and the carbon nanotube film comprises a first end and a second endopposite to the first end, in the process of graphitizing the carbonlayer, the first end is connected to the carbon nanotube array, and thesecond end is held by a supporting shaft.
 16. The method of claim 15,further comprising pulling the carbon nanotube film into a first room,and supplying a carrier gas and the carbon source gas to the first roomto form the carbon layer in the first room.
 17. The method of claim 15,further comprising making the carbon nanotube film with the carbon layerinto a second room, and heating the second room to a temperature fromabout 2000 degrees Celsius to about 3000 degrees Celsius forgraphitizing the carbon layer.
 18. The method of claim 15, furthercomprising depositing a plurality of conductive particles aftergraphitizing the carbon layer.